Details are emerging on the sole suspect in Florida's Marjory Stoneman Douglas High School shooting, Nicolas Cruz, who was a problem teen previously expelled from the school, with a love of guns.

First clear picture of Florida high school shooting suspect, Nikolas Cruz, as he hwas taken down by police outside Marjory Stoneman Douglas High School.

Source: WSVN-TV

Seventeen students and teachers are dead and at least 14 have been taken to hospital, with three in critical condition, after today's mass shooting.

Cruz is 19-years-old had been expelled from Florida's Marjory Stoneman Douglas High School for disciplinary reasons.

A family member of the suspect Cruz told ABC News in the US that Nikolas was adopted by Roger and Lynda Cruz, both of whom are now deceased, and that his adopted mother died last year.

He had one AR-15 semi-automatic style firearm and multiple magazines, and was taken into custody after the shooting.

One Marjory Stoneman Douglas student said Cruz was kown within the school as troubled, and carried "multiple guns" on him.

"He got kicked out of school last year, he always had guns on him and stuff like that so he was a little bit of a troubled kid, he always had jokes on it like that," the student said outside the school.

"It was a lot of crazy stuff that he did, just not right for school. He got kicked out of school multiple times for that kind of stuff.

"He carried multiple guns, he showed me his guns. Actually I got kicked out of school myself and he showed me what guns he had, he showed me personally.

"And a lot of the times the kids wouldn't pick on him for that kind of stuff because they knew what could go on, they were scared."

The suspected shooter Cruz was found off campus this morning (NZT), with reports he blended into fleeing students to escape to a nearby suburb where he was captured by police.

It's the second worst in US school history, eclipsing the infamous Columbine shooting, which left 15 dead including the two shooters in 1999.

Florida student Zackary Wells said he didn't know the suspected shooter personally, but said he was a former student and understood he "would regularly post videos of him with guns and knives and things like that".

"I had seen him before, but had not really talked to him or known him at all," he told US ABC.

"One of my friends said that he used to follow him on social media accounts where he would regularly post videos of him with guns and knives."

Mr Wells said to US ABC the suspected shooter was a former student.

"One of my teachers said something about him either transferring or being kicked out of the school, I'm not sure which it was but yes, he did used to go to our school."

Aerials above the Marjory Stoneman Douglas High School in Parkland show dozens of police vehicles.
Source: Associated Press

He believed the suspected shooter "dropped his rifle and he made his way out with the other students that were being evacuated. He walked on over to Windham Lake and he was accosted a quarter mile from my area."

"One of the kids in that class, good friends with him, was on the phone with police officers and they gave information of his name and we looked for his name in a book and found a picture of him in a school composite photo," he said to US ABC.